CONSTRUCTION AND RATINGS OF HIGH VOLTAGE CIRCUIT BREAKERS BASIC INFORMATION

HIGH-VOLTAGE CIRCUIT BREAKER
CONSTRUCTION

All high-voltage circuit breakers have

# Contacts that operate at system
voltage

# Insulation between main contacts and
ground potential (porcelain, oil, or gas)

# Operating and supervisory devices

# Insulated links between the operating
devices and the main contacts

Most power circuit breakers are opened
and closed automatically by remote control. Various kinds of
operating mechanisms are used. Among them are AC or DC solenoids,
compressed air, high-pressure oil, springs, or electric motors.

Circuit interruption occurs when a
plasma arc with temperatures exceeding 20,000 K appears for a short
time interval between the main contacts. This occurs when the current
passes zero, and it is determined by the time relationship between
the buildup of dielectric strength of the gap between the open
contacts and the rise of transient recovery voltage.

The interrupting capacity of a circuit
breaker, measured in kilovolt-amperes (kVA), is the product of the
phase-to-ground voltage in kilovolts (kV) of the circuit and the
interrupting ability, in amperes (A), at stated intervals and for a
specific number of operations. The current is the root-mean-square
(rms) value existing during the first half-cycle of arc between
contacts during the opening stroke.